Process Priority with nice
A regular user starts a long compression job with nice -n 10 xz big.tar, then tries to speed it up with renice -n 0 -p <pid>. The command fails with Permission denied. Why?
nice -n 10 xz big.tar
renice -n 0 -p <pid>
Choose one answer
renice only works on processes started without nice.
renice
nice
Niceness values must be negative for renice; 0 is not allowed.
Unprivileged users can only raise a process's niceness (lower its priority), never lower it back.
The process must be stopped with kill -STOP before its priority can change.
kill -STOP